Title

Investigations of Mammalian Cytochrome P450 2B4 in Surfactant Films James M. Gillan and Katharine D. Hagen

Document Type

Article

Publication Date

2005

Abstract

We report thermodynamic properties of the drug-metabolizing human cytochrome P450 2B4 within surfactant films based on electrochemical methods. The protein was embedded in didodecyldimethylammonium bromide (DDAB) bilayer film on a basal plane graphite electrode. Cyclic voltammetry at 25 mV/s was conducted in 50 mM KPi 50 mM KCl pH 7.0 buffer anaerobically between 18.4-40.4 ?C. Analysis of the half-wave potential dependence on temperature revealed decreases in entropy and enthalpy upon heme reduction. These thermodynamic changes are coupled to the expulsion of the heme distal axial water ligand; this is indicative of hydrophobic collapse around the catalytic center, resulting in a more rigid and stable structure. Spectroscopic analysis of the protein in the film revealed the FeIII heme Soret band at 418 nm, identical to its value in solution. This confirms protein integrity within the film, thereby affirming the physiological relevance of our thermodynamic data.

Advisor

Michael G. Hill

Department

chem

Support

National Science Foundation - Research Experience for Undergraduates Grant; Howard Hughes Medical Institute Undergraduate Science Education Grant

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